This invention relates to sensor systems for detecting analytes in fluids.
The development of chemical sensors has been the focus of intense research since the 1960s. Recently, conjugated polymers have received considerable attention for use in sensor applications, both as electronic conductors and as active sensing elements with ligands coupled to the polymer backbone. Poly(aniline), in particular, has received attention due to its proton coupled redox chemistry and its resulting pH dependant properties. For example, poly(aniline) has been used as a pH electrode and has been coupled to reactions that generate or consume protons to create sensors.
In general, in one aspect, the invention features methods for detecting analytes in a fluid. According to the methods, a sensor is provided that includes a polymer capable of undergoing a proton-coupled redox reaction, which polymer includes a plurality of reactive substituents capable of undergoing a reaction with an analyte. The sensor is exposed to a fluid containing the analyte, and a response is detected based on a change in the pKa of the polymer.
In general, in another aspect, the invention features non-enzymatic sensor systems for detecting an analyte in a fluid. The systems include a fluid volume, a sensor in operable contact with the fluid volume, and a detector configured to detect a response when the sensor is exposed to a fluid in the fluid volume. The sensor includes a substrate having a surface, and a sensor film deposited on the substrate surface. The sensor film includes a polymer capable of undergoing a proton-coupled redox reaction. The polymer includes a plurality of reactive substituents capable of undergoing a reaction with an analyte. The response is detected based on a change in the pKa of the polymer.
Particular embodiments can include one or more of the following features. The plurality of reactive substituents can include two or more chemically different reactive substituents. The two or more chemically different reactive substituents can have selectivity for different analytes and/or different effects on the pKa of the polymer. One or more of the reactive substituents can have an inductive effect and/or a resonance effect on the pKa of the polymer. The analyte can react with one or more of the reactive substituents upon exposure of the sensor film to the fluid to cause a change in the pKa of the polymer.
The sensor can include one or more conjugated polymers. At least one of the conjugated polymers can be selected from the group consisting of polyaniline, poly(o-phenylenediamine), poly(o-aminophenol), polyphenoxazine, polyphenothiazine, and poly(aminonaphtalene). The polymer can be a functionalized polyaniline, such as a poly(aniline boronic acid) (e.g., a homopolymer of 3-aminophenylboronic acid).
At least a plurality of the reactive substituents can be selected from the group consisting of boronic acids, pyridines, bipyridines and thiols. The analyte can be selected from the group consisting of polyols, fluorides, and amines. The analyte can be a metal selected from the group of metals capable of forming a complex with a ligand selected from the group consisting of pyridines, bipyridines and thiols. One or more of the reactive substituents can be capable of undergoing a reversible or irreversible reaction with the analyte. The polymer can be a poly(aniline boronic acid), and the analyte a polyol.
The response can be a change in the electrochemical potential of the sensor relative to a reference electrode, or a change in pH, conductivity, impedance, color, or mass of the sensor.
The analyte can be identified based on the detected response. Where one or more of the reactive substituents is capable of reacting with a plurality of different analytes, the analyte can be identified by distinguishing between at least one analyte in the fluid and at least one of the plurality of different analytes capable of reacting with the reactive substituents based on the detected response. Similarly, where one or more of the reactive substituents is capable of reacting with a plurality of different analytes, the analyte can be identified by distinguishing between a plurality of different analytes in the fluid based on the detected response. The concentration of the analyte in the fluid, or a change in that concentration, can be identified based on the detected response. If the sensor is exposed to the fluid for a time sufficient to allow the reaction between the reactive substituents and the analyte to reach an equilibrium, the response can be measured at the equilibrium.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.